1. Field of the Invention
The present invention relates to methods and devices for treating spinal conditions, and more particularly, to methods and devices for modifying intervertebral disc tissue.
2. Description of Related Art
A variety of devices and methods are known in the art for treating pain in the human spine. Of such devices, many are directed to relieving pain arising from intervertebral disc abnormalities. Intervertebral disc abnormalities are common in the population and cause considerable pain, particularly if they affect adjacent nerves. Disc abnormalities result from trauma, wear, metabolic disorders and the aging process and include degenerative discs, localized tears or fissures in the annulus fibrosus, localized disc herniations with contained or escaped extrusions, and chronic, circumferential bulging discs. Disc fissures occur as a degeneration of fibrous components of the annulus fibrosus. Rather minor activities such as sneezing, bending or simple attrition can tear degenerated annulus fibers and create a fissure. The fissures may be further complicated by extrusion of nucleus pulposus material into or beyond the annulus fibrosus. Difficulties can still present even when there is no visible extrusion, due to biochemicals within the disc irritating surrounding structures and nerves.
A contained disc herniation is not associated with free nucleus fragments migrating to the spinal canal. However, a contained disc herniation can still protrude and irritate surrounding structures, for example by applying pressure to spinal nerves. Escaped nucleus pulposus can chemically irritate neural structures. Current treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nucleotomy. Complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height. It has been proposed to treat weakening due to nucleus pulposus deficiency by inserting preformed hydrogel implants.
More recently, delivery of in situ curing liquids to form a solid prosthetic in the nucleus of a disc have been disclosed. The fluid form of these implants enables access to the spine in a minimally invasive manner, and includes procedures for restoring structural integrity to vertebral bodies. There are a variety of injectable biomaterials known in the art including: cross-linkable silk elastin copolymer, protein hydrogel, polyurethane-filled balloons, collagen-PEG, chitosan, and other polymers.
Delivery of an in situ forming prosthetic to the nuclear space requires constructing a passageway into the nucleus and removal of the nucleus fibrosus, in total or in part. The passageway is usually made through the annulus, especially when part of the annulus needs to be removed to correct a pathological condition. Whether the passageway is through the annulus or elsewhere, for example, through the vertebral body, there is a risk of the formed nucleus prosthetic extruding out through the passageway into which it is introduced. Nucleus prosthetic extrusion can affect the surrounding nerves adversely. Methods of blocking a passageway made through the annulus include, for example, enclosing the prosthetic entirely inside of an enveloping sheath. Still other methods of preventing nuclear prosthetic extrusion include delivering a preformed prosthetic in a reduced state, which when introduced into the body increases in volume.
U.S. Patent Application Publication No. 2009/0024107, to Wilson et al., describes a device for blocking a passageway made through the annulus to prevent extrusion of implant material. A catheter balloon is introduced into the annulus opening flush with the interior space of the annulus while implant material is injected through an axially located catheter running through the interior of the catheter balloon. This technique can block extrusion of the implant material through the opening of the annulus, however it does not provide a positive anchor of the delivery apparatus. Therefore, it is necessary for the user of the device to devote constant attention to prevent accidental removal of the catheter balloon during the procedure. If the device is accidentally removed from the annulus during the procedure, not only will there be difficulty in repositioning the device at the opening of the annulus, but implant material can freely exit the opening of the annulus, giving rise to further complications.
This typically means that one hand of the user is constantly tied up just to maintain the position of the device. This is a problem, when for example, two hands are required to attach a syringe of implant material to the applicator during a procedure. Even when the user manages to maintain the position of the device using one hand, difficulties can arise if, for example, the user's other hand is also tied up with actuating the injection of the implant. In such situations, the user will not have any hand free for other necessary tasks that may arise during the procedure.
The conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there still remains a continued need in the art for methods and devices that can provide improved blocking of disc implant material from extrusion out the opening of a vertebral disc annulus while providing improved anchoring of a delivery device to the opening of the annulus. There also remains a need in the art for such methods and devices that are easy to make and use. The present invention provides a solution for these problems.